DESCRIPTION: (Applicant's Abstract) Although medications for treating opiate addiction are now available, the basic biology underlying the physiologic changes induced by chronic opiate use is unknown. New techniques utilizing principles of molecular biology have now become available, and will be used for the identification of genes involved in the addiction processes. Mice and rats will be treated chronically with morphine to induce addiction. Some mice will be treated concurrently with either N-methyl-D-aspartate (NMDA) antagonists or nitric oxide synthase (NOS) inhibitors, compounds shown to clock tolerance development and withdrawal. After tolerance development, and its inhibition is demonstrated, RNA from appropriate animals will be isolated and subject to either differential display, representational difference analysis (RDA), or gene discovery array membrane hybridization in order to identify genes modulated by morphine administration and to test the hypothesis that the modulation can be attenuated by the inhibitors. Genes identified as being appropriately modulated will be investigated to determine localization of the mRNA, the time course of morphine and antagonist treatment required to induce alterations in gene expression , and opioid pharmacology sufficient to mediate similar changes in gene expression. In addition, antisense oligonucleotides will be utilized to investigate the requirement for the gene products for tolerance and dependence. RNA derived from animals treated chronically with morphine and/or NMDA or NOS antagonists will be tested to determine whether genes known to be modified by chronic morphine, such as adenylyl cylase, are returned to control levels by the additional treatment with the antagonist. An improved knowledge of the molecular processes involved in tolerance and addiction will increase the likelihood that medications can be developed for the treatment of addicts and other patients.